Porous member with penetrating channels for fluid flow therethrough and a method of producing the member

ABSTRACT

According to the present invention, a porous member made of temperature-resistant material for filtering and/or mixing fluids comprises first channels ( 132 ) and second channels ( 138 ) respectively extending therethrough. The channels extend under an acute angle to the flow direction (D). Fluids flowing through the porous member ( 101 ) flow through the channels ( 132, 138 ), on the one hand, and, on the other hand, through the porous material between the channels so that a good mixing of the fluids is obtained and a fluid, homogenized over the cross section, exits from an outlet surface ( 103 ). The invention further refers to methods of making the porous member ( 101 ), wherein, according to the present invention, a foamed plastic material member is formed with channels, the foamed material member is wetted with wetting material and is afterwards removed by evaporation during the curing.

BACKGROUND OF THE INVENTION

A porous member with penetrating channels for fluid flow therethroughand a method for producing the member The invention refers to a porousmember of temperature-resistant material having channels extendingtherethrough through which a fluid (gas and/or liquid) may pass, and toa method for producing this member.

Such members are used, for example, as chemical mixers. The conventionalchemical mixers consist of corrugated sheets of steel or ceramicfabrics. These abutting steel sheets or ceramic fabrics are comprisedinto units with crossing channels forming between the steel sheets orthe fabrics. Sometimes the steel sheets are perforated so that a fluidflow passing through this chemical mixer member is homogenized, therebymixing the fluid. For reasons of production, the individual mixermembers cannot be produced with more than a certain maximum length.Thus, for producing longer mixers, a plurality of such mixer members arearranged in line. This increases the cost of the production process.

SUMMARY OF THE INVENTION

It is the object of the invention to provide a porous member withpenetrating channels through which fluid may flow, wherein thehomogenization and mixing of the fluid is improved, and to providesimplified methods of producing such a member, substantially independentof the length of the porous member.

The present porous member of temperature-resistant material has an inletsurface and an outlet surface The fluid flowing through the porousmember enters the porous member at the inlet surface and leaves theporous member at the outlet surface so that flow direction runs from theinlet surface towards the outlet surface. According to the invention,the porous member is provided with first channels extending under anacute angle to the flow direction. In the following, an acute angle isan angle other than 0°. Due to the porosity of the member, the channelspenetrating the member are in communication so that a mixing of thefluid flowing through the porous member occurs. Since the channels forman acute angle with the flow direction, a part of the fluid flowsthrough the channels and a part of the fluid flows in the flow directionthrough the porous portions, i.e., the porous walls between the channelsimmediately in the flow direction. Thus, the fluid (or several fluids)is mixed and homogenized so that a homogenized fluid exits from theoutlet surface of the porous member.

Since the porous member is temperature-resistant, it is suited formixing hot fluids. In doing so, due to the present structure of themember, no local overheating occurs that could damage or destroy theporous member.

Moreover, the present porous member is suited for filtering fluids.

Here, particles are deposited on the walls of the pores. Due to thetemperature resistance of the member, which is made, for example, fromhigh temperature-resistant ceramics such as zirconia oxide or siliconcarbide, the member used for filtering may be cleaned by burning,whereby the residual filtered matter is combusted. This does not damagethe filter. In particular, the present porous member is simultaneouslysuited for mixing and filtering fluids.

Depending on the shape of the porous member and the position of theinlet and outlet surfaces, the flow direction varies. For example, in acylindrical member whose end faces are the inlet and outlet surfaces,respectively, the flow direction is straight. In a bent or otherwiseshaped porous member, the center line of the member corresponds to theflow direction so that the flow direction varies in the longitudinaldirection of the member.

Preferably, besides the first channels, the porous member has secondchannels that are also arranged under an acute angle to the flowdirection and, in addition, are arranged under an angle to the firstchannels, i.e. an angle other than 0°. Such crossing channels that maypenetrate each other at least partly, improve the homogenization andmixing of the Fluids. A further improvement may be achieved by varyingthe angle of the channels to the flow direction along the extension ofthe channels. In a cylindrical porous member with a continuous flowdirection over the length of the member from the inlet to the outletsurface, the channels are wavy or zigzag-shaped, for example. Thus, aportion of the fluid flowing through the member that is sufficient tohomogenize the fluid, flows through the porous portions.

The channels of the porous member are preferably arranged in rows, atleast one row of first channels and a row of second channels beingprovided, and the channel rows being arranged alternating side-by-sideand in parallel.

In a preferred embodiment, the porous member is cylindrical and thefirst and/or second channels extend from the inlet surface to the outletsurface of the member. Here, cylindrical means a longitudinal memberwith parallel end faces having the same, but an optional contour.Depending on the conditions of the device in which the porous member isused, the contour may be a curve or a polygon, for example.

Besides the usefulness of the porous member as a chemical mixer formixing fluids and as a filter for filtering particles from fluids, thepresent porous member can also be used, in particular, in the combustionchamber of a pore burner.

Pore burners have a housing with an inlet and an outlet, a mixture ofgas and air flowing into the pore burner through the inlet and the fluegases being exhausted from the pore burner through the outlet. Prior toignition, the gas-air mixture flows in the flow direction of the poreburner and through a backfire means. As the backfire means, aconventional flame retention baffle or a plate with holes may beprovided, for example. The backfire means prevents the gas-air mixtureburning behind the backfire means, seen in the flow direction, frombackfiring towards the inlet opening. The backfire means is followed bythe combustion chamber in which the gas-air mixture is ignited by anignition means and burned therein. Pore burners are characterized inthat the combustion chamber accommodates a heat-resistant porousmaterial in which the gas-air mixture is combusted. Thus, a more uniformcombustion of the gas-air mixture is obtained so that within a largeeffective range of the pore burner, only small amounts of pollutantssuch as NO_(x) or CO are produced during combustion. Using the presentporous member in the combustion chamber of the pore burner, the emissionof pollutants is reduced further. Thus, even at one thirtieth of thenominal power of the pore burner, a clean combustion is obtained. Thepore burner is particularly suited for use in heating installations.

A further use of the porous member, according to the invention, is itsimplementation as a heat accumulator. Due to the porous structure of themember and the channels extending therethrough, the fluid flowingthrough the porous member is distributed homogeneously over the crosssection of the member so that, when hot fluid flows through the member,the heat is received homogeneously by the porous member. When coolerfluid passes through subsequently, the heat uniformly transferred fromthe porous member to the fluid so that a uniform heating of the fluidoccurs. Therefore, the present porous member is very well suited for useas a short- and medium-term heat accumulator.

In particular, the porous member is suited for use as a heat accumulatorin regenerative radiant burners. Regenerative radiant burners serve toheat material, for example, steel ingots, by thermal radiation. Here,two radiant burners operating at intervals are employed. Each burner isprovided with a porous member as the heat accumulator. Further, a bloweror suction device is provided which, at intervals, either supplies theburners with a mixture of fuel and air or fresh air or exhausts the fluegases. During the first cycle, the blower directs fresh air or a mixtureof gas and air through the heat exchanger of the first burner to thecombustion head, where the fresh air is either mixed with fuel andignited or the mixture of fuel and air is ignited directly. In the firstcycle, the burner flame of the first burner heats the material locatedabove the burner by radiant heat. In the meantime, the flue gases areexhausted through the heat exchanger of the second burner, heating thesame up. To this end, the same blower or a separate suction device canbe used. In the second cycle, the function of the two burners isinterchanged so that fresh air or a gas-air mixture is passed throughthe heat exchanger of the second burner and heated up in the process.The heated gas-air mixture is ignited in the combustion head of thesecond burner. In the second cycle, the material is heated by theradiant heat of the flame of the second burner and the flue gases areexhausted through the heat exchanger of the first burner. By providingthe heat accumulators in each of the two burners, the gas-air mixture orthe fresh air is pre-heated so that the efficiency of the radiantburners is increased significantly. The use of the porous members oftemperature-resistant material, preferably ceramics, as provided by theinvention, prevents local damages to the heat exchanger even at veryhigh temperatures. Using the porous member as a heat accumulator, it ispossible to pre-heat the fresh air to about 1000° C. Moreover, theporous members serve as exhaust gas filters.

For manufacturing the porous member of temperature-resistant material,in particular ceramics, with channels extending through the member, theinvention proposes a method, wherein, according to a first variant

at least one insert member is placed in a mold, the insert memberdefining the course and the shape of at least one channel,

a foamed plastic material is introduced into the mold so that the atleast one insert member is embedded in the foamed plastic materialmember which is flexible after curing,

the foamed plastic material member is removed from the mold and the atleast one insert member is removed from the foamed plastic materialmember,

the surface of the foamed plastic material member is wetted with acurable temperature-resistant wetting material, and

the foamed plastic material of the foamed plastic material member wettedwith wetting material is removed by heating the same so that a porousmember made from the wetting material and adapted to be flown through bya fluid is obtained.

It is the principle idea of the present method to first provide aflexible foamed material structure with channels running therethrough.According to the invention, this is done by providing foamed plasticmaterial around an insert member representing the course of the laterchannel and by embedding the same therein. Alternatively, a plurality ofsuch insert members may be used. The insert members may have a structurechanging in all three dimensions so that eventually not only straight,but also curved, wavy or zigzag-shaped channels may be produced. Thefoamed plastic material is flexible after curing so that the insertmembers can be pulled from the foamed plastic material. Thereafter, afoamed plastic material member is left through which extend one or aplurality of straight or curved channels, the channels being incommunication due to the porous structure of the foamed plasticmaterial. The foamed plastic material suitably is an open-cell or aclosed-cell material. In particular, polyurethane is used as the foamedplastic material.

After the insert member(s) has (have) been removed from the foamedplastic material member, the foamed plastic material member is wettedwith a wetting material. This wetting can be imagined as a wetting ofthe entire surface of the structure of each foamed plastic materialmember with the wetting material. Preferably, the wetting material isslip, in particular ceramic slip. It is of general importance that thewetting material is cured so that after curing a self-supporting wettedfoamed plastic material member is obtained, the dimensional stabilityand the self-supporting ability thereof being provided by the wettingmaterial. Thus, the porous member thus formed includes, on the one hand,the channels with their inner walls wetted with the wetting materialand, on the other hand, the connections between adjacent channels alsowetted on their inner walls. Subsequently, this foamed material memberwetted with hardened wetting material is heated to a degree that thefoamed plastic material is removed by burning. An alternative method ofremoving the foamed plastic material is the evaporation resulting, forexample, from a chemical reaction with a corresponding process gas.

In the manner described above, porous members with channels and withoptional length may be made, even when the channels have undercuts orsimilar three-dimensionally varying paths. Such a member may be employedas a catalyst, if, for example, a catalytically active layer is applied.With or without this additional layer, it may anyway be used as achemical mixer homogenizing a fluid mixture flow passing through,thereby mixing the fluids. It is a further advantage of such a mixer (aporous member with channels running therethrough) that it has only a lowflow resistance. Of course, one would obtain a fluid flow rate with aporous member, causing, however, a much greater flow resistance thanwith a porous member produced according to the above method. Likewise,the present porous member may be used as a filter. Since the porousmember is made of temperature-resistant material, the filter may becleaned by burning.

According to a second variant of the invention, the porous member oftemperature-resistant material, in particular ceramics, penetrated bychannels and adapted to be flown through by fluid may be produced by

producing a wavy flexible mat of foamed plastic material,

winding the mat into a foamed plastic material member,

wetting the surface of the foamed plastic material member with a curabletemperature-resistant wetting material, and

removing the foamed plastic material of the foamed plastic materialmember wetted with wetting material by heating the same, so that aporous member made from the temperature-resistant wetting material andadapted to be flown through by a fluid is obtained.

With this production variant, a wavy flexible mat of open-cell or closedcell foamed plastic material is produced which is then rolled into a(wound) member. The foamed plastic material member thus formed ispenetrated by channels that are formed between the valleys and the peaksof adjacent windings of the wavy flexible mat. For example, the woundmember retains its wound structure by using an adhesive.

The insert members may be rigid or, preferably, flexible and/orinflatable. After the foamed plastic material member has been produced,the insert members inflated until then may be deflated or relaxed so asto be removed from the foamed plastic material member. Should the insertmembers not be inflatable, but flexible, they may readily be pulled fromthe foamed material due to their flexibility.

After the forming of the wound member, another wetting withtemperature-resistant wetting material is performed, the material beingallowed to cure. Thereafter, the member thus made is heated to removethe foamed plastic material. The advantages to be obtained with theporous member of this variant are identical to those described for thefirst variant of the invention. In addition, the manufacturing processof the second manufacturing variant is simpler since no insert membersare embedded in the foamed plastic material member that have to bewithdrawn from the cured, but still flexible foamed plastic material.

It is true for both variants of the invention that the wetting materialpreferably is slip, in particular ceramic slip. The wetting step isperformed by drenching the foamed plastic material member with thewetting material. These methods are known per se from the production ofceramic foams. The ceramic slip is cured by burning. At the same time,the foamed plastic material is removed by evaporation.

Further, it is true for both above described variants of the inventionthat the foamed plastic material member wetted with the wetting materialis cured. Since the foamed plastic material member is still flexiblewhile the wetting material is not yet cured, it may be placed in bent orotherwise shaped molds (molds for connector pipes, for example, or thelike) to then cure in these molds. Thus, the finished product has ashape that allows a compact mounting in a mixer or filter assembly or apipeline of a mixer or filter assembly. Finally, it is suitable to makethe insert members and the mold from material inert to the foamedmaterial or to provide it with a coating of inert material.

For producing a porous member of temperature-resistant material, inparticular ceramics, adapted to be passed through by fluid and beingprovided with channels extending therethrough, the invention proposesthe following method as a third variant, wherein

at least one foamed plastic material member with a top and a bottomsurface is formed from a flexible foamed plastic material,

the foamed material member being sheared in a first direction about ashear angle by being subjected to a first shearing force,

from the top and/or the bottom surface, first channels are formed in thefoamed plastic material member thus sheared, the channels being formedunder an angle to the normal of the top and/or bottom surface, thisangle being different from the first shear angle,

the first shearing force is relaxed and the foamed plastic materialmember restores itself,

the surface of the foamed plastic material member is wetted with acurable temperature-resistant wetting material, and

the plastic material of the foamed plastic material member wetted withthe wetting material is removed.

The essential idea this method is based on is to first provide theflexible foamed plastic material structure with channels extendingtherethrough. For an improved mixing of the fluid passing through themember, these channels extend obliquely to the axial extension of themember. One could form these oblique channels under an angle other than90° to the top or bottom surface of the foamed material structure or thefoamed material member. This, however, makes the production process moredifficult, which is due in particular to the flexible structure of thefoamed material member. Therefore, in this third variant of making thepresent porous member, it is proposed to shear the foamed materialmember, i.e., to subject the foamed material member to shearing forces.Now, the channels may be formed under an angle of 90°, in particular, tothe top or bottom surface of the sheared foamed material member. Whenthe shearing force acting on the foamed material member is subsequentlyrelaxed so that the foamed material member is in its relaxed state, thechannels extending through the foamed material member are oblique.

In the manner described above, first channels extending in a firstdirection may be formed in a foamed plastic material member.Subsequently, the foamed material member, according to the first andsecond variant, is wetted with temperature-resistant wetting materialand the foamed plastic material member is removed.

When the foamed plastic material member is sheared in another directionafter the forming of the first channels, which direction is preferablyopposite to the active direction of the previously applied shearingforce, second channels may be formed in the foamed material memberextending through the foamed material member in a direction differentfrom that of the first channels. Thus, two groups of channels runthrough the foamed plastic material member, having differentorientations.

Depending on the magnitude of the shearing forces and their effectivedirections, channels with different degrees of inclination may be formedin a formed plastic material member. The orientation of the channelsalso depends on the angle under which they are formed in the shearedfoamed member.

The process steps of shearing the foamed plastic material member and offorming channels can also be performed simultaneously. To this end, forexample, a punching tool may be set on the top or the bottom surface ofthe undeformed foamed member which is not yet subjected to shearingforces. As soon as the punching tool contacts one side of the foamedmember, it is displaced relative to the opposite side of the foamedplastic material member so that shearing forces act on the foamedmember. The punching is performed either upon reaching the desired shearangle or already during shearing. Thus, it is sufficient to displace thepunching tool during punching, relative to the opposite side of thefoamed member so that shearing forces act on the foamed member.

For the channels to be punched in the foamed member to have a possiblycircular section, the foamed member may be pressed prior to or after thepunching, whereby it is compressed.

In a fourth variant of the process, the channels are formed in a foamedmember without shearing the same. In this variant, first channels areformed in an outer surface of a foamed member. Subsequently, the foamedmember is cut, the cutting surface extending under an acute angle to thelongitudinal extension of the first channels. A foamed member thus cutcan be processed further, until a plate material is obtained havingparallel top and bottom surfaces, one surface being defined by thecutting surface.

In the variant described above, second channels may be formed in thecutting surface after the cutting of the foamed plastic material member,whereupon the foamed plastic material member is cut again such that thiscutting surface extends under an acute angle to all of the channels.When the foamed plastic material member thus cut is processed further sothat a plate material or foamed material blocks are obtained, a foamedmaterial structure is produced that is run through by channels extendingoblique to each other and that has parallel top and bottom surfaces, atleast one of which is defined by the (second) cutting surface.Thereafter, the foamed plastic material member is again wetted withwetting material, as described above, and the foamed plastic materialmember is removed.

In the most general form, this advantageous production method accordingto the third and fourth variants provides a foamed material structurethrough which oblique channels extend, wherein groups of these channelsextend in parallel and the channels may be subdivided into a pluralityof groups of channels with different relative orientations.

Suitably, a plurality of thus produced foamed material members aresuperimposed, wetted and cured, the foamed plastic material member beingremoved during curing, so that a member can be produced through whichfluid may flow and which has properties of a mixer, all this withoutrestrictions in length incurred by the manufacturing process. Theindividual foamed material members are preferably made as a platematerial of random geometric shape with parallel top and bottomsurfaces.

The channels are preferably formed by punching the foamed materialmember. Such a punching tool comprises two pressing members frictionallycontacting the top and bottom surfaces of the foamed material member.When these two pressing members have been brought into frictionalengagement with the foamed plastic material member, at least onepressing member is moved relative to the other so that the foamedplastic material member arranged therebetween is sheared. Now, thepunching tool can be moved into the foamed plastic material member.Here, it is feasible to compress the sheared foamed plastic materialmember by moving the pressing members toward each other, such that theholes may be formed by means of punching tools.

It is further suitable to have perforated pressing members so that thepunching tools may be advanced through the holes into the foamed plasticmaterial member. In the state in which the foamed plastic materialmember is punched, the holes of the two pressing means should be flush.

Thus, the third and fourth variants of the present method provides forthe production of a porous member through which a fluid can flow, themember comprising either a single foamed plastic material member orseveral superposed foamed plastic material members which or each ofwhich has one channel or a plurality of channels extending under acommon oblique angle or under different oblique angles. Due to theporous structure of the foamed plastic material member, these channelsare interconnected. When using a plurality of foamed plastic materialmembers, it is suitable to have different, in particular oppositelydirected, orientations of the adjoining channels of adjacent foamedmaterial members.

Suitably, the foamed plastic material is an open-cell or a closed-cellmaterial. In particular, polyurethane is used as the foamed plasticmaterial.

When a plurality of adjoining foamed plastic material members areprovided with wetting material, it is suitable to interconnect thefoamed plastic material members before wetting. Here, it is feasible toweld the foamed plastic material members together by heating theircontact surfaces. An alternative to this connection is to coupleadjacent foamed plastic material members by means of the cured wettingmaterial.

Since the foamed plastic material member or the group of successivefoamed plastic material members is still flexible with the wettingmaterial not yet cured, it can be placed in curved or otherwise shapedmolds (such as manifold molds or the like) to be cured in these molds byburning. Thus, the finished product is given a shape that allows for acompact installation in a mixer device or a tubing of such a mixerdevice.

The present invention allows to produce ceramic mixers that arecharacterized by an excellent mixing of the fluid flowing therethrough.When a porous member produced according to the invention is used, forexample, to mix the combustion gases of an internal combustion engine,as, for example in a motor vehicle, a catalyst also used therein may bearranged closer to the outlet valves of the internal combustion enginethan was possible up to now. The catalysts presently used, inparticular, in vehicle production, are supposed to have a minimumdistance from the outlet valves of the internal combustion engine,because a sufficiently well mixture of the combustion gases occurs onlyat a certain distance after the outlet valves so that their cleaning bythe catalyst is satisfying. A mixer produced according to the presentinvention, however, makes it possible to reduce the distance between thecatalyst and the outlet valves of the internal combustion engine. Thisis advantageous with a view to the cleaning of the combustion gases,since the combustion gases now flow into the catalyst at a highertemperature.

In the present method, it should be underlined as being particularlyadvantageous that for producing the foamed plastic material members, theconventional production methods for foams may be used. The foams, mostlycoming as blocks, merely have to be processed to plate material whichwill then be sheared in accordance with the present invention so as toform the channels. The production of block foam is rather economic sothat, after all, also the rigid members to be flown through by a fluidcan be made at relatively low cost, making use, in particular, of thewell-known technology of foam production. In particular, no specialmolds are required for the foam production. Thus, the production processof the present invention uses a semi-finished material, i.e. foamedplastic plate material which is available at extremely low cost. Alsothe further method steps, especially the forming of the oblique channelsis done, according to the present invention, in a simple and, in view ofproduction technology, economic manner.

The following is a detailed description of the preferred embodiments ofthe present porous member and the methods of its production, made withreference to the accompanying drawings. In the Figures:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of a first embodiment of aporous member according to the present invention,

FIG. 2 is a schematic sectional view of the porous member of FIG. 1,taken along line II—II,

FIG. 3 is a schematic perspective sectional view of a second embodimentof the porous member according to the present invention,

FIG. 4 is a schematic sectional view of the porous member illustrated inFIG. 3,

FIGS. 5 to 9 are illustrations of the individual production steps forforming a foamed plastic material member penetrated by oblique channelsfrom which the porous member illustrated in FIGS. 1 and 2 is made,

FIGS. 10 and 11 illustrate the molds and insert members necessary forproducing a flexible foamed plastic material member with penetratingchannels for making a further embodiment of the present porous member,

FIGS. 12 and 13 illustrate the production of a flexible foamed plasticmaterial member with penetrating channels, i.e. by winding, to makeanother embodiment of the present porous member,

FIGS. 14 to 18 illustrate the individual production steps for forming afoamed plastic material member penetrated by oblique channels for thesubsequent production of another embodiment of the porous member,

FIG. 19 is a sectional view through a foamed material member formed froma plurality of foamed plastic material members according to FIGS. 14 to18,

FIG. 20 is a perspective view of a foamed plastic material member,partly broken away,

FIGS. 21 to 24 are schematic illustrations of the individual productionsteps for forming a foamed plastic material member penetrated by obliquechannels according to an alternative production method,

FIG. 25 is a schematic illustration of a pore burner with a porousmember arranged in the heating chamber thereof, and

FIGS. 26 and 27 are schematic illustrations of the two cycles of aregenerative radiant burner wherein porous members are used as heataccumulators.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 and 2 illustrate a first embodiment of a porous member 1. Theporous member has wavy first channels 2 and second channels 3 thatextend from an inlet surface 4 to an outlet surface 5. The channels 2are located in the sectional plane of FIG. 1 and the channels 3 arebehind this sectional plane. The wave-shape of the channels 2 and 3 isidentical. The channels 2 and 3 are arranged offset with respect to eachother so that the wave-shapes extend in opposite senses, i.e. they arenot parallel in the longitudinal direction of the channels 2, 3. Amedium flowing through the porous member 1, seen in the flow directionD, enters the porous member 1 at the inlet surface 4 and exits at theoutlet surface 5. To homogenize the fluid, the wavy channels 2, 3 forman acute angle with the flow direction D over their entire extension.The channels 2, 3 extend along the center lines of the channels 2, 3from the inlet surface 4 to the outlet surface 5. Since the channels 2,3 are wavy, the acute angle varies relative to the flow direction D, theangle being 0 at each apex of the individual curves. Since the angle is0 only at the apexes, but otherwise always is an acute angle other than0° between the flow direction D and the extension of the channels 2, 3,a good mixing and homogenization of the fluids occurs. Since porousmaterial 6 is provided between the channels, the fluid not only flowsthrough the channels 2, 3, but also through the porous material 6 of theporous member 1 so that a connection is given between the channels 2, 3.

The second channels 3 are offset relative to the first channels 2 sothat, seen in the flow direction D, an angle other than 0° existsbetween the channels 2, 3.

A further connection between the channels 3 or the channels 2 existswithin a respective channel row (FIG. 2). The production of the porousmember illustrated in FIGS. 1 and 2 will be described with reference toFIGS. 5 to 9.

FIGS. 3 and 4 illustrate a second embodiment of a porous member 101according to the present invention. The porous member 101 is penetratedby first channels 132 and second channels 138 from an inlet surface 102towards an outlet surface 103. The channels 132, 138 always extend underan acute angle to the flow direction D. Since the channels 138, 132 arezigzag-shaped, the angle of the channels 132, 138 varies relative to theflow direction D along the extension of the channels 132, 138, i.e.along the center line of the channels 132, 138. The porous member 101,which is circular cylindrical seen in the flow direction D, may besubdivided into a plurality of sections 104, 105 (FIG. 4). Within thesesections, the first channels 132 and the second channels 138 are alwaysstraight, the first channels 132 forming an angle of about 90° to thesecond channels 138 and an acute angle of about 45° to the flowdirection D.

The sections 104, 105 may also be formed adjoining each other such thatthe channels 132, 138 of adjacent sections are offset but notzigzag-shaped. Fluid flowing through the channels 132, 138 of a section104, 105 is thus forced to flow through a porous portion before reachinga channel 132, 138 of the adjacent section. At the bordering surfaces ofadjacent sections, the channels may also partly overlap.

At the bordering surfaces of two adjacent sections 104, 105, the angleof the first channels 132 and the second channels 138 change. In theexample illustrated in FIGS. 3 and 4, the change in angle is about 90°.Preferably, the change in angle is <90° so that an acute angle appearsbetween the channels. The sections 104 and 105 are identical so that thesections 104, 105 recur periodically in the flow direction D. With anangle of about 90° between the channels in the contact surface of twoadjacent sections 104, 105, the porous member 101 may be composed ofidentical parts. Here, the individual parts are arranged such thatadjacent sections 104, 105 are mirror-inverted to the contact surface.Thus, the production of the individual sections is substantiallysimplified. The production of the porous member 101 will be describedwith reference to FIGS. 14 to 20.

FIG. 5 is a longitudinal section through a cylindrical mold 10 formed bya sleeve 12 and a bottom member 14 closing one of the front endsthereof. A plurality of serpentine-shaped substantially beads 16 projectfrom the bottom member 14 which, as is particularly evident from FIG. 6,are arranged side by side in a plurality of parallel rows 18. Theserpentine-shaped beads 16 of each row 18 are interconnected by thinconnecting webs 20. Like the beads 16, these thin connecting webs 20extend over the entire axial length of the mold 10. Further, these thinconnecting webs 20 extend from the beads 16 adjacent the sleeve 12 tothe inner wall of the sleeve 12. The bottom plate 14 with its projectingbeads 16 and the connecting webs 20 forms an insert member 22 forinsertion into the sleeve 12 of the mold 10.

As is particularly evident from FIG. 6, cavities 24 are formed betweenadjacent rows 18 of beads 16 and connecting webs 20. In the steprepresented in FIG. 7, these cavities 24 are filled with a PU foamedplastic material 26. This foamed plastic material 26 remains flexibleeven after curing so that the entire insert member 22 can be pulled fromthe mold 10, as illustrated in FIG. 9. In this manner, a shaped PUmember 28 is formed that has throughgoing channels 30, the path of whichis determined by the extension of the beads 16.

Alternatively, it may be provided to remove the foamed plastic material26 from the sleeve 12 together with the insert members 22 still embeddedtherein, and to remove the insert members 22 from the foamed plasticmaterial 26 only subsequently. In principle, it can be a furtheradvantage to design the sleeve 12 as two parts to facilitate the removalof the foamed plastic material 26, eventually together with the insertmembers 22.

Subsequently, this shaped PU member 28 is taken from the sleeve 12 ofthe mold 11 and drenched with ceramic slip. After the curing of theceramic slip, the ceramic member is heated so that the foamed plasticmaterial is removed by evaporation. The finished product then is aceramic material porous member (FIGS. 1 and 2) penetrated by individualchannels 30 which are in fluid communication with each other due to theporous structure of the ceramic material.

FIGS. 10 and 11 illustrate an alternative mold 10′ to the mold 10, theformer having a cylindrical wall 12. From one of the two front ends, aplurality of insert members 24′ is placed into the mold 10′, the insertmembers comprising a straight and narrow strip-shaped bottom member 14′with a plurality of projecting serpentine-shaped beads 16′ that arecylindrical in section. The individual serpentine-shaped beads 16′ maybe interconnected by continuous webs, however, this is not imperative.As is visible in FIG. 11, the individual strip-shaped insert members 14′abut closely, thereby filling the entire cross section of the sleeve 12′of the mold 10′.

The technique of producing a ceramic foamed material member using themold 10′ of FIGS. 10 and 11 is performed analogously to the method ofproduction described for FIGS. 5 to 9. After the foamed plastic materialhas cured, while it is still flexible, the individual insert members 24′are pulled out. The foamed plastic material member thus obtained is thenwetted with ceramic slip by drenching so as to be heated after curing inorder to remove the foamed plastic material.

FIGS. 12 and 13 represent another alternative to the method ofproduction of a ceramic foamed material member.

This production variant first provides for creating a wavy mat 40 offlexible foamed plastic material. This mat 40 has angularly extendingstraight recesses 42 and raised portions 44. Winding the mat 40 into awound member 46 (see FIG. 9) yields a structure of foamed plasticmaterial penetrated in its axial direction by a plurality of channels48. The wound member 46 is fixed in its shape particularly by means ofadhesive and is wetted with ceramic slip. The ceramic foam thus obtainedafter curing is heated to remove the plastic material by evaporation.

The methods for producing a porous member according to the invention,described in connection with FIGS. 14 to 24, use foamed material whichis produced in blocks in standard production sizes (for example, 60m×1.5 m×0.8 m). In particular, this foamed material is closed-cellmaterial processed in a second process known per se with controlledpressure waves or explosions so that the closed cells of the foamedmaterial are opened. Thus, a block of foamed material with open pores isobtained.

This foamed material block is cut, for example, to foamed material mats110 (also referred to above as foamed material member or foamed plasticmaterial member) of 25 mm in thickness (plate material). According tothe method of FIGS. 14 to 18, each of these mats 110 is placed into atool 112 comprising two parallel perforated pressing or contact plates114, 116 adapted to be approached and moved apart. The upper perforatedplate 114 contacts the top surface 118 of the foamed material mat 110,while the lower perforated plate 116 contacts the bottom surface 120 ofthe foamed material mat 110. This situation is depicted in FIG. 14.

By moving at least one of the perforated plates 114, 116 in the plane oftheir extension, the foamed material mat 110 is sheared as illustratedin FIG. 15 To this end, the plates 114, 116 must contact the foamedmaterial mat 110 with a certain static friction. It is possible, forexample, to provide the plates 114, 116 with thorns or similarprojections that penetrate into the top or bottom surface 118, 120 wherethey hook.

After relative displacement of the two plates 114, 116, the holes 122 inthe upper plate 114 are flush with the holes 124 provided in the lowerplate 116. Thereafter, the plates 114, 116 are approached so that thefoamed material mat 110 therebetween is compressed in the sheared stateby elastic deforming (not illustrated in the Figs.). Now, a punchingtool 126 may be advanced through the coincident holes 122, 124 and thefoamed material mat 110 provided therebetween. The punching tool 126comprises a support plate 128 with, in particular, tubular cutting orpunching elements 130 projecting from the support plate 128 according tothe pattern and the arrangement of the holes 122 and 124. Using thesecutting and punching elements 130, first channels 132 may be formed inthe sheared foamed material mat 110, as illustrated in FIG. 15.

After this process, the two pressing plates 114, 116 are returned totheir home positions so that the foamed material mat 110 again takes itsinitial shape (relaxed state). As illustrated in FIG. 16, the channels132 formed in the direction of the normal to the top and bottom surfaces118, 120 of the sheared foamed material mat 110 now extend obliquely,the angle depending on the shearing previously applied to the mat 110.

Thus, the process described above unwinds such that the foamed materialmat 110 is first more or less strongly compressed by the pressing plates114, 116 and sheared to take a trapezoidal shape. Then, the punching isperformed in the direction of the normal to the top and bottom surfacesof the foamed material mat 110. After the withdrawal of the punchingtool 126 and after the foamed material mat 110 has relaxed, channels 132are provided therein with an orientation under an angle to the normal ofthe top and bottom surfaces of the foamed material mat 110.

According to the above process, a first group of first channels 132arranged in a plurality of first rows 134 are formed in the foamedmaterial mat 110. A plurality of second channel rows 136 with secondchannels 138 orientated opposite to the previous channel rows 134, arecreated by shearing the foamed material mat 110 between the pressingplates 114, 116 in the direction opposite to that of the former step andby subsequently forming the channels 132 using the punching tool 126that is moved transverse to the traveling direction of the pressingplates 114, 116 (FIG. 17). Thus, the foamed material mat 110 may beprovided with a plurality of adjacent rows 134, 136 of channels 132,134, the first channels 132 of one and the same row extending inparallel, while the second channels 138 of adjacent rows 136 areorientated in the opposite direction.

Pieces are cut from the foamed material mats 110 made according to theabove described method, the shape of which corresponds to the crosssection of the member through which fluid is to flow. For example,cylindrical members 140 may be cut from the foamed material mats 110(FIG. 20). In FIG. 19, a plurality of such cylindrical members 140 areabutted axially so that the arrangement of cylindrical members 142 thusobtained is penetrated by channels that, in portions, run in zigzag and,thus, in opposite senses.

In a further step, the entire structure 142 is wetted with slip that iscured subsequently. The cured slip connects the individual cylindricalpieces 140 which form a single unit, namely the porous member (FIGS. 3and 4). The slick is burned out so that a member is obtained that ismade of ceramic foamed material. This member has no plastic material onitself, since the same evaporates during burning.

An alternative production process for making a foamed material member110′ with penetrating first and second channels 132, 138 is described inthe following in connection with the schematic illustrations in FIGS. 21to 24. Starting from a block foam material 144, first channels 132 areformed in one of its outer surfaces 146. These channels 132 extendsubstantially at right angles to the extension of the outer surface 146in which they are formed. Subsequently, the foamed block 144 is cutalong line 148. After rotation of the cut foamed block 144 in thedirection of the arrow 150 in FIG. 21, the situation of FIG. 22 isobtained, in which the cutting surface 152 defined by the cuttingsurface 148 is arranged on top and extends under an acute angle to theextension for the first channels 132.

According to FIG. 21, second channels 138 are then formed in thiscutting surface 152, which channels in turn extend substantially atright angles to the cutting surface 152. Thereafter, the foamed block144 thus penetrated by the first and second channels 132, 138 is cutalong the line 154. After rotation of the thus cut foamed block 144 inthe direction of the arrow 156, the situation illustrated in FIG. 24 isobtained, where the cutting surface 158 resulting at the cutting surface154 is on top. By suitable trimming, the foamed material mat 110′ isobtained that is penetrated by crossing first and second channels 132,138.

The foamed member thus produced is then wetted with slip and cured.

The above described porous member of temperature-resistant, inparticular ceramic material is particularly suited for use in a poreburner (FIG. 25). Such pore burners are employed in heatinginstallations, for example, since the nominal capacity of pore burnerscan be adjusted over large ranges with low emission of pollutants. Apore burner comprises a housing 200 with an inlet 202 and an outlet 204.A mixture of gas and air is supplied to the pore burner via the inlet202. The mixture of gas and air reaches a pre-chamber 206 of the housing200 and then flows through a flame retention baffle or a plate withholes 208. The flame retention baffle 208 serves as a backfire meansthat prevents the flames from backfiring into the prechamber 206. Afterhaving passed the flame retention baffle 208, the mixture of gas and airreaches a combustion chamber 210, where it is ignited by an ignitionmeans 212. For the homogenization of the combustion in the combustionchamber 210, a porous member 101 according to the present invention islocated therein. The example of a pore burner illustrated in FIG. 25uses a porous member 101 illustrated in FIGS. 3 and 4. One may also useanother embodiment of the porous member.

When exhausting the combustion gases from the combustion chamber 210,the combustion gases pass by a heat exchanger 214 and exhausted throughthe outlet 204. A heat transfer fluid flows through the heat exchanger214. When the pore burner is used in conventional heating installations,the heat exchanger 214 is connected directly with the water circuit ofthe heating installation.

FIGS. 26 and 27 respectively illustrate the first and the second cycleof a radiant burner. Radiant burners are used to heat stock material220, such as steel ingots. The two radiant burners 222, 224 areidentical in structure, each having a burner head 226 to which fuel issupplied through a supply line 228. In the burner head 226, the fuel isgasified and ignited.

In the first cycle (FIG. 26), the fresh air is supplied to a pre-chamber232 of the radiant burner 224 via a line 230. The pre-chamber 232accommodates a porous member according to the invention that serves as aheat exchanger 234. The fresh air flows through the heat exchanger 234into the burner head 236. The fresh air supply to the pre-chamber 232 iseffected in the direction of the arrows 240 through a blower andcorrespondingly controlled valves 236, 238.

The radiant heat emitted by the flame 242 heats stock material 220. Theflue gases occurring during combustion are drawn into the burner head226 of the radiant burner 222 and passed through the heat exchanger 234of the radiant burner 222. In the process, the heat exchanger 234 isheated by the flue gases. The flue gases are exhausted in the directionof the arrows 244, a valve 246 being controlled accordingly so that nomixing of the fresh air supplied to the radiant burner 224 and the fluegases exhausted through the radiant burner 222 occurs.

In the second cycle (FIG. 27), the functions of the two radiant burners222, 224 are switched. The radiant burner 222 is supplied with fresh airin the direction of the arrows 248, the valves 238 and 246 beingcontrolled correspondingly. The fresh air reaches the prechamber 232 ofthe radiant burner 222 and is passed through the heat exchanger 234,heating up in the process. In the burner head 226 of the radiant burner222, the fresh air serves to gasify the fuel supplied through the supplyline 228. The mixture of gas and air is then ignited so that the radiantheat of the flame 250 again heats the stock material 220. By preheatingthe fresh air, the efficiency of the radiant burner can be increasedsignificantly.

In the second cycle (FIG. 27), the flue gases are exhausted through theradiant burner 224 with the heat exchanger 234 of the radiant burner 224being heated. Thereafter, the flue gases are exhausted in the directionof the arrows 252, the valve 236 being controlled accordingly. Aftertermination of the second cycle, the radiant burners 222, 224 are againoperated in the first cycle so that an interval operation is performedin which the fresh air supplied to the respective radiant burner ispreheated.

Although a preferred embodiment of the invention has been specificallyillustrated and described herein, it is to be understood that minorvariations may be made in the apparatus without departing from thespirit and scope of the invention, as defined the appended claims.

I claim:
 1. A member for filtering or mixing fluids comprising a body oftemperature-resistant porous ceramic foam material, said porous bodyhaving a planar inlet surface (102) and an opposite planar outletsurface (103), a plurality of channels (132, 138) extending between saidinlet and outlet surfaces (102, 103, respectively) through which fluidis adapted to flow in a flow direction (D) from said inlet surface (102)to said outlet surface (103), said plurality of channels (132, 138)including a first plurality of channels (132) and a second plurality ofchannels (138), and said first plurality and second plurality ofchannels (132, 138, respectively) being located in immediately adjacentalternating substantially parallel planes and in crossing relationshipto each other from plane-to-plane as viewed normal to said planes. 2.The member as defined in claim 1 wherein each channel of said firstplurality and second plurality of channels (132, 138, respectively) aredisposed at an acute angle to the flow direction (D).
 3. The member asdefined in claim 1 wherein the channels of at least one of the firstplurality of channels (132) and the second plurality of channels (138)are in parallel relationship to each other.
 4. The member as defined inclaim 1 wherein the channels of each of the first plurality of channels(132) and the second plurality of channels (138) are in parallelrelationship to each other.
 5. The member as defined in claim 1 whereinat least some of said channels are of a cylindrical cross-sectionalconfiguration.
 6. The member as defined in claim 1 wherein the porousbody is made of zirconia oxide.
 7. The member as defined in claim 1wherein the porous body is made of silicon carbide.
 8. The member asdefined in claim 1 including another body of temperature-resistantporous ceramic foam material, said another porous body having an inletsurface (102) and an opposite outlet surface (103), a plurality ofchannels (132, 138) extending between said last-mentioned inlet andoutlet surfaces (102, 103, respectively) through which fluid is adaptedto flow in said flow direction (D) from said last-mentioned inletsurface (102) to said last-mentioned outlet surface (103), saidlast-mentioned plurality of channels (132, 138) including a firstplurality of channels (132) and a second plurality of channels (138),said last-mentioned first plurality and said last-mentioned secondplurality of-channels (132, 138, respectively) being located inimmediately adjacent alternating substantially parallel planes and incrossing relationship to each other as viewed normal to saidlast-mentioned planes, and said first-mentioned porous body and saidanother porous body being disposed with their respective outlet andinlet surfaces (102, 103) contiguous each other and with the respectivefirst-mentioned and last-mentioned plurality of channels (102, 103,respectively) being disposed in fluid communication with each other. 9.The member as defined in claim 2 wherein the channels of at least one ofthe first plurality of channels (132) and the second plurality ofchannels (138) are in parallel relationship to each other.
 10. Themember as defined in claim 2 wherein the channels of each of the firstplurality of channels (132) and the second plurality of channels (138)are in parallel relationship to each other.
 11. The member as defined inclaim 2 wherein at least some of said channels are of a cylindricalcross-sectional configuration.
 12. The member as defined in claim 3wherein at least some of said channels are of a cylindricalcross-sectional configuration.
 13. The member as defined in claim 4wherein at least some of said channels are of a cylindricalcross-sectional configuration.
 14. A method of manufacturing a porousmember of temperature resistant material for filtering or mixing fluidscomprising the steps of: (a) providing a member made of porous flexiblefoamed plastic material including opposite outer surfaces disposed in afirst position relative to each other, (b) applying a first shear forceto the porous member causing relative spacial displacement of the outersurfaces from the first relative position in a first directionsubstantially parallel to the direction of shear force application to asecond relative position, (c) forming a first plurality of spacedopenings through the porous member while the first and second outersurfaces are in the second relative position thereof, (d) restoring theporous member to its presheared condition, (e) applying a second shearforce to the porous member causing relative spacial displacement of theouter surfaces from the first direction and substantially parallel tothe direction of shear force application to a relative position, (f)forming a second plurality of spaced openings through the porous memberwhile the first and second outer surfaces are in the third relativeposition thereof, (g) restoring the porous member to its preshearedcondition at which the first and second plurality of openings are incrossing relationship to each other, (h) wetting the porous member witha temperature resistant material, and (i) curing the temperatureresistant material to form a porous member of temperature resistantmaterial for filtering or mixing fluids.
 15. The method as defined inclaim 14 wherein forming steps (c) and (f) are performed in alternatingspaced substantially parallel planes.
 16. The method as defined in claim14 wherein the first plurality of spaced openings are in substantiallyparallel relationship to each other.
 17. The method as defined in claim14 wherein the second plurality of spaced openings are in substantiallyparallel relationship to each other.
 18. The method as defined in claim14 wherein the first plurality of spaced openings are in substantiallyparallel relationship to each other, and the second plurality of spacedopenings are in substantially parallel relationship to each other. 19.The method as defined in claim 14 wherein each ofthe second and thirdrelative positions are located a substantially identical distance fromthe first relative position.
 20. The method as defined in claim 14wherein one of the second and third relative positions is located adifferent distance from the first relative position as compared toanother of the second and third relative positions relative to the firstrelative position.
 21. The method as defined in claim 14 wherein atleast one of said first and second plurality of openings defines anacute angle to one of said first and second outer surfaces after theperformance of restoring step (g).
 22. The method as defined in claim 14wherein each of said first and second plurality of openings define anacute angle to one of said first and second outer surfaces after theperformance of restoring step (g).
 23. The method as defined in claim 15wherein the first plurality of spaced openings are in substantiallyparallel relationship to each other.
 24. The method as defined in claim15 wherein the second plurality of spaced openings are in substantiallyparallel relationship to each other.
 25. The method as defined in claim15 wherein the first plurality of spaced openings are in substantiallyparallel relationship to each other, and the second plurality of spacedopenings are in substantially parallel relationship to each other. 26.The method as defined in claim 15 wherein each ofthe second and thirdrelative positions are located a substantially identical distance fromthe first relative position.
 27. The method as defined in claim 15wherein one of the second and third relative positions is located adifferent distance from the first relative position as compared toanother of the second and third relative positions relative to the firstrelative position.
 28. The method as defined in claim 15 wherein atleast one of said first and second plurality of openings defines anacute angle to one of said first and second outer surfaces after theperformance of restoring step (g).
 29. The method as defined in claim 15wherein each of said first and second plurality of openings define anacute angle to one of said first and second outer surfaces after theperformance of restoring step (g).
 30. The method as defined in claim 23wherein each of the second and third relative positions are located asubstantially identical distance from the first relative position. 31.The method as defined in claim 23 wherein one of the second and thirdrelative positions is located a different distance from the firstrelative position as compared to another of the second and thirdrelative positions relative to the first relative position.
 32. Themethod as defined in claim 23 wherein at least one of said first andsecond plurality of openings defines an acute angle to one of said firstand second outer surfaces after the performance of restoring step (g).33. The method as defined in claim 23 wherein each of said first andsecond plurality of openings define an acute angle to one of said firstand second outer surfaces after the performance of restoring step (g).